Thing is, I don't trust you because I don't know you. If I'm not ahead pulling more, there's generally a reason for it - in pugs for example, I generally pull 2-3 packs depending on the dungeon and wait to pull more later on once I'm sure the healer can actually handle it. There have been plenty of dungeons where even that was too much, and even using cooldowns wasn't enough to keep me alive.
If you want bigger pulls, say something. If you wanna just yank me around the dungeon without taking the two seconds it takes to say "you can pull bigger," all that's gonna do is annoy me tbqh.
Granted I also haven't had any real issues with rescue. If I'm tanking, I'm generally queuing with people I know anyway, and it doesn't bother me as much because I know my friends know what they're doing. If I die we can laugh about it in voice chat :P pug healers, though? I don't know you, I don't know your skill level, and I don't know your intentions. Speak up. It's clearer and less likely to irritate people.